Usually Tails is installed to a USB flash drive, or one can still download an ISO and put that on optical media, then boot that. There are instructions on the Tails site. My disclaimer is that I have used Tails for several years, and different versions. I do not own a Librem ( I have not won the lottery yet.) I am working on trying to install the Pure OS onto one of several other computers. They are being disagreeable, wrong hardware, boot problems.
After one installs Tails onto the first USB (or was that what you were doing?) Then one inserts another USB flash drive to install the Live Tails onto the second drive. The second drive can have an "Persistent File, information that is kept.
You can leave the Pure OS on computer, and boot the Tails on a USB drive. As Tails is meant to be anonymous, it (in the past) was considered to be more secure to not modify Tails. Then you would always boot a fresh install of the OS. Now the folks who have created Tails to allow one to install other software. and have a Persistent file on the same USB.
You may be ahead of me, and the issue might be that Tails might not have a driver for the Librem computer wireless adapter. But it does not make sense that the WiFi would crash in the middle of the install.
Anyway, my thoughts; Try to install Tails the way it has always been in the past, with two flash drives as described on the Tails website. Perhaps clone it back over to Librem hard drive. (hmm, that might not be a good idea, usually one does not clone an OS to an SDD-used to be – someone got better knowledge?) Perhaps try to run Tails in a Virtual machine in the Pure OS?
I have been interested in using Tails as installed on primary hard drive, then just using that from the standpoint that the folks who do Tails keep up with all the Debian Security enhancements, and also do some testing. I see other Security OS’s that are maintained by one or two people. Testing seeming to be haphazard. So I am interested in what you find out about installing Tails onto hard drive. So please come back here and keep let me know what you find out.